基于快速傅里叶变换的低功耗两线制涡街流量计

以超低功耗单片机MSP430为核心,研制数字涡街流量计。通过硬件的改进,提高了系统抗50Hz工频干扰的能力。采用周期图法处理涡街流量传感器输出信号,同时进行频谱的幅值和频率校正,提高频率计算的精度。采用汇编语言实现实数FFT算法,提高运算速度和减少内存容量,使单片机可以实时实现数字信号处理方法。对功率谱进行平均,同时通过设置队列对流量平稳和流量跳变的情况进行处理,增加了计算结果的稳定性,同时提高了系统响应速度。计算瞬时和累积流量,输出4~20mA直流电流。实验结果表明,系统具有较强的现场抗干扰能力,较高的测量精度和较宽的量程比,同时又实现了低功耗和两线制工作。

Vortex flowmeter with low power and two-wires based on FFT

A super low power MCU-MSP430 is used as the core of processing system to developed a digital vortex flowmeter.The ability of rejecting 50Hz power interference is enhanced by the improvement of hardware.The periodogram spectral analysis is adopted to process the output signal of vortex flow sensor,and the amplitude and frequency of the spectrum are corrected to improve the accuracy of frequency calculation.Real FFT algorithm is implemented by assemble language to speed up the computation and the memory space is reduced,which makes the digital signal processing method run in MCU in real time.The results of power spectrum are averaged,and at the same time the situation of steady flow and jumping flow are treated by setting up queue to improve the stability of calculation results and increase the speed of response.Both transient and total flow-rates are calculated,and the direct current 4-20 mA[0] is output.The experimental results show that the system has strong rejecting-disturbance ability,high measurement precision and large turn-down ratio,and at the same time,the meter runs in the low power and two-wire mode.